The present invention relates to door closure apparatus for use with doors of safety storage cabinets, such as cabinets for storing flammable or combustible material. More particularly, the present invention relates to apparatus for automatically closing the storage cabinet door in the event of elevated ambient temperatures before the temperature reaches the ignition point of the stored materials, either to prevent ignition of the combustible materials or contain the combustion thereof. The present invention particularly relates to door closure apparatus for use with hinged folding-type doors, particularly bifold doors.
Safety storage cabinets or compartments for combustible materials and automatic door closure means therefor have been in existence for many years. Also, automatic door closure means for closing doors or the like in the event of elevated temperatures are well known.
One type of prior art apparatus is disclosed in U.S. Pat. No. Re. 27,066, issued to C. E. Williams on Feb. 16, 1971. In the Williams arrangement a bifold door is spring biased toward its closed position and is manually latchable in its folded open position by means of a fusible latch member. That arrangement is disadvantageous because the latch member is hidden on top of the door in its open position, making access very cumbersome. This is inconvenient because the latch must be manually actuated each time the door is closed. Furthermore, the Williams device requires two hands to latch the door in its open position, one to hold the door open against the urging of the bias spring, and the other hand for operating the latch mechanism. Because of the inaccessible location of the fusible latch member and its method of mounting, replacement of it is also inconvenient after it has once been melted in use. Additionally, Williams uses a special fusible link design which would have to receive special approval of the interested authorities before use.
A somewhat similar arrangement is disclosed in U.S. Pat. No. 122,615 issued to G. H. Knight on Jan. 9, 1872. Knight discloses fusible latch mechanism for use on shutters and overcomes one disadvantage of the Williams arrangement in that the Knight shutters can be latched open with the use of only one hand. However, like the Williams device, replacement of the Knight latch once it has melted is extremely difficult, requiring a resoldering operation. Furthermore, Knight's shutter latch is designed to be partially mounted on an associated wall, and adaptation of it to a free standing cabinet would require opening of the doors at least 270 degrees to engage the latch. Furthermore, the Knight arrangement is not suitable for use with folding doors and the latch placement at the bottom of the shutter, while relatively accessible, is disadvantageous because the highest temperatures will be experienced at the top of the shutters.
Another type of closure arrangement is disclosed in U.S. Pat. No. 3,683,551, issued to H. Y. Martindill on Aug. 15, 1972. The Martindill device is representative of a number of similar arrangements which utilize a separate door driving mechanism which is thermally actuated automatically to close the door but which, when not in use, does not impede manual opening and closing of the door. This arrangement is complicated, cumbersome and expensive, since it must generate sufficient force to drive the entire door to its closed position. Furthermore, these arrangements are not suitable for use with folding doors.
Still another type of prior art system is disclosed in British Pat. No. 824,133 issued on Nov. 25, 1959. In this arrangement doors which are biased toward a closed position are frictionally held in an open position by a thermally releasable brake mechanism. While manual operation of the door is possible, such operation must overcome the frictional force applied by the brake mechanism. Furthermore, this arrangement does not permit the door to be positively latched in its open position. Finally, this arrangement is not readily adaptable for use with folding-type doors.